Format

Send to

Choose Destination
See comment in PubMed Commons below
J Biol Rhythms. 1993;8 Suppl:S99-108.

Preliminary studies on the immediate phase-shifting effects of light and exercise on the human circadian clock.

Author information

1
Department of Medicine, University of Chicago, Illinois 60637.

Abstract

The aim of the present research was to determine the magnitude and direction of immediate phase shifts of human rhythms following a single exposure to a 3-hr pulse of bright light or physical activity. The pulse of light or activity was presented under "constant-routine" conditions, and measurements of the resultant phase shifts were performed under the same constant-routine conditions on the first day following pulse presentation. Four overt rhythms that are strongly dependent on circadian timing--namely, the rhythms of plasma cortisol, plasma thyroid-stimulating hormone (TSH), plasma melatonin, and body temperature--were monitored. The analysis of the TSH profiles indicated that exposure to light at about the time of the minimum of body temperature resulted in phase advances averaging less than 1 hr in magnitude. Exposure to light approximately 3 hr before the time of the minimum of body temperature resulted in phase delays of 1-2 hr. Preliminary analyses of the melatonin profiles have confirmed these observations. Our findings regarding the effects of exercise are still inconclusive.

PMID:
8274769
[Indexed for MEDLINE]
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Loading ...
    Support Center